Ill jump in, it's the 100K Rk in the cathode follower David is refering to. Blencowe does an analysis of the DC coupled cathode follower, which can be biased to permanently draw grid current and exhibit compression and 2nd harmonic distortion.
It's very interesting and Blencowe highlights an effect of the DC coupled follower that is seldom mentioned elsewhere (at least I've never read it elsewhere).
www.valvewizard.co.uk
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David Root
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Re: www.valvewizard.co.uk
That's right Ears, I was referring to the cathode follower.
In the rebuild I'm just tying up, I am using 6SL7s instead of 12AX7, so I reduced both 100Ks in V2 to 68K based on the 6SL7 nominal plate resistance being ~70% of a 12AX7, (44K vs. 62.5K) based on Mr. B.'s writing that a lower plate resistance tube would need a lower cathode resistor to maintain the compression effect. I didn't do a before and after audio check but it sounds good now.
Thanx for the welcome Markus. It's actually welcome back to Canada, my wife and I are both dual citizens.
In the rebuild I'm just tying up, I am using 6SL7s instead of 12AX7, so I reduced both 100Ks in V2 to 68K based on the 6SL7 nominal plate resistance being ~70% of a 12AX7, (44K vs. 62.5K) based on Mr. B.'s writing that a lower plate resistance tube would need a lower cathode resistor to maintain the compression effect. I didn't do a before and after audio check but it sounds good now.
Thanx for the welcome Markus. It's actually welcome back to Canada, my wife and I are both dual citizens.